This invention is related in general to networks and more specifically relates to digital networks and accompanying systems and methods for improving network performance and reliability.
Digital networks are employed in various demanding applications including military, university, and business applications. Such applications often demand reliable high-performance networks that are not easily destabilized when changes in network topology occur.
Systems for improving or optimizing network performance are particularly important in large networks, which often have many routers connected in various configurations that can lead to network inefficiencies. An exemplary network may exhibit hub-and-spoke topology, wherein a centralized distribution router, called the hub router, is connected to plural remote routers, called spoke routers, at the edge of the network. In such a network, the spoke routers may be connected to smaller networks, called end networks, that are not connected to other outside networks except through the hub router. Such spoke routers are often called stub routers. Certain routing protocols, such as Enhanced Interior Gateway Routing Protocol (EIGRP) employ a stub-routing feature to enhance network efficiency and stability in large hub-and-spoke networks employing large numbers of neighboring spoke routers.
In the exemplary network, Internet Protocol (IP) traffic passes through a hub router to the stub routers and to the end networks. The hub router may be further connected to the Internet or other network. A given hub router may be connected to hundreds of stub routers via one or more interfaces, called spoke or stub interfaces. For the purposes of the present discussion, a hub router may connect to plural stub routers at a single interface, called the stub interface of the hub router.
A stub router often does not provide the hub router with alternate routes to other parts of the network. Accordingly, a hub router employing a stub-routing feature will suppress route queries on stub interfaces between the hub router and stub routers to prevent multicast queries from the hub router from causing stuck-in-active scenarios. A stuck-in-active scenario occurs when a router query goes unanswered before the query is cancelled and resent by the sending router.
Furthermore, routers that are configured as stub routers must forward or bounce all non-local traffic to a hub router. Consequently, stub routers often lack complete routing tables. Generally, the hub router provides only default route information to a stub router.
Since route-sharing communications are limited on the stub interface between the hub router and accompanying stub routers, the stub interface can accommodate more stub routers than otherwise possible if the stub routers were not configured as stub routers. If a spoke router that is not configured as a stub router is connected to the hub router via a stub interface, the stub interface will then be treated as a non-stub interface. Consequently, the hub router will issue queries to the large numbers of stub routers via the stub interface, which may cause a query storm, clog the stub interface, destabilize the network, and prevent network convergence.
Accordingly, interfaces between hub routers and many stub routers are often excessively vulnerable to configuration mistakes. For example, accidentally configuring a spoke router as a non-stub router or adding a spoke router without first configuring the spoke router as a stub router could destabilize the network.